An adventure into the wonderful world of vintage audio restoration and collecting.

Sunday, December 29, 2013

Yamaha Natural Sound CA-610 Stereo Amplifier

Another cool cat from the 70's. Yamaha's 1977 mid range CA-610 from its 'Natural Sound' series is a 40 WPC amplifier that sounds a lot bigger than the 40 watts it's supposed to produce and better than you may expect. On top of that it has some great looks with its brushed aluminum and wood grain veneer. A well rounded amplifier, with all the functionality most will need.

This unit came from the same lot as the previously blogged Sansui AU-101. Functionally it was in the 'OK' range for its age. The switches and pots had all dried up and was quite a bit scratchy, nothing a good clean and service could handle.

Just opened up, a little dusty but nothing serious.

The main challenge was with the cosmetic condition of the knobs and switches. Yamaha elected to have all toggle switches made of plastic with aluminum paint on top for that brushed look. Which gave that slightly cheap 'clunk' feeling when switching them. However the rotating switches were made from solid billets of aluminum. When you rotate the speaker, or input selectors it feels solid and responsive, just what you want. The volume knob is also made of solid aluminum, which is just wonderful to turn! It just feels right.

But after years of toggling and turning, then abandonment, they wear, get grimy and worst of all start to oxidise. Where solid aluminum is used it's not so bad and can be saved with proper techniques, but with plastic it bubbles from the underside and care needs to be taken not to remove the original finish.

All the knobs removed, ready for cleaning. Click on the image for a higher resolution image.

The new cleaning method i'm using is with an ultrasonic cleaner. This allows for non-abrasive cleaning which can damage the already fragile surface of the plastic switches. It's also very useful for getting the dirt and grime that's trapped in the grooves of the machined aluminum knobs. Some detergent and an hour in the cleaner will provide results like below.

The front faceplate was in pretty good condition to start off with, but while all the knobs were removed the opportunity was seized to clean that up aswell. No fancy tricks just a bit of elbow work.

Back on the electronics front, all capacitors were replaced using Panasonic capacitors. There were no faulty transistors which made the work pretty smooth sailing. Switches and potentiometers were all cleaned thoroughly.

All cleaned up and ready to go.

If you're looking for an integrated amplifier with plenty of features and enough power to drive some mid sized speakers, the CA-610 is a good fit. Its sound is a lot bigger than the specifications on paper.

Hi Greg, the meter lights were actually replaced as they had both burnt out. Due to its design, there is very little ventilation for incandescent bulbs and as such burnt out pretty quickly or weakened/melted the plastic housings- a hindrance to the available technology at the time. The lamps in this unit were replaced with white LEDs driven through a bridge rectifier.

When incandescent lamps were used, they would give out a warm yellow color, to create a white light, a light blue filter would need to be put between the light source and what was to be illuminated. In this case, I've left the blue filter in place to give this amplifier a unique look with a cool white with a slight tint of blue color. However if you wanted to, all you would need to do is remove the blue filter and it would illuminate in pure white, better than what the original designers could have envisioned when the amplifier was produced.